[The ERA characteristics in normal-hearing persons].

The ERA characteristics (amplitudes and latencies) were measured in normal-hearing adults (20 to 25 years of age) at frequencies of 500 Hz, 1000 Hz and 4 000 Hz. Two other age groups (30 to 50 and 55 to 70 years of age) were measured only at 1 000 Hz. Contrary to other authors, the linear scale was chosen to represent the amplitudes. In calculating the variances of the amplitudes it turned out that the intra-individual variance is significantly below the inter-individual variance. Expressed in per cent as a variational coefficient, both decrease with increasing stimulus intensity. Contrary to the behaviour of the amplitudes, no significant difference between the intra- and inter-individual variational coefficient of the latencies could be found. The same is valid for the variational coefficients of the N1 and P2 latencies. As a function of the stimulus strength, the variational coefficient passes through a minimum at medium stimulus intensity. Within the investigated range of 20 to 70 years of age, no significant differences of amplitudes and latencies between the age groups could be found.